Integrated circuits are continually being built and interconnected in denser and more complex packages. These circuits are being used to address high technology electronic applications and often include circuits that are designed to operate at high frequencies and at relatively high power levels. For example, many high performance digital computers are being implemented using VLSI (very large scale integration) circuits.
When used in a relatively dense electronic package, this type of circuitry must meet rigidly defined electrical and mechanical specifications. These specifications include line impedance, continuity, and minimal noise and cross-talk (cross-coupling) interferences.
Increasing device density has led to a decrease in the spacing between adjacent metal lines. Therefore, in deep-submicron technologies, cross-talk between parallel wires in the same wiring plane and between planes becomes increasingly important.
As metal lines are formed closer together, the potential for such capacitive and inductive interference between the lines increases. This interference is particularly troublesome when high frequency signals are propagated over adjacent lines in respective signal channels. The reliability of the electrical communication is thus reduced because the cross-talk acts as a source of noise which may introduce error in the communication.
Typically, adjacent wiring planes preferably have non-parallel wiring directions which reduces cross-talk to a negligible amount. However, planes i and i+2, i.e., a plane and the next but one plane, typically run in parallel direction and could generate cross-coupling.